Since the method for synthesizing a carbon cluster (hereinafter also referred to as “fullerene”), in which carbon atoms are arranged to form a spherical shape or a rugby ball shape, was established, fullerene has been energetically studied. As a result many fullerene derivatives have been synthesized.
With respect to specific examples of such fullerene derivatives, methods for synthesizing a fullerene derivative, in which 5 organic groups bind to a fullerene skeleton (hereinafter also just referred to as “penta(organo)fullerene derivative”), have been reported (e.g., Japanese Laid-Open Patent Publication No. Hei 10-167994 (Patent document 1); Japanese Laid-Open Patent Publication No. Hei 11-255509 (Patent document 2); J. Am. Chem. Soc., 118, 12850 (1996) Son-patent document 1); Org. Lett., 2, 1919 (2000) (Non-patent document 2); and Chem. Lett., 1098 (2000) (Non-patent document 3)).
As a method for producing a penta(organo)fullerene derivative, for example, it is known that, by reacting an organocopper reagent prepared using a phenyl Grignard reagent and CuBr.S(CH3)2 with fullerene C60, a phenylated fullerene derivative, in which phenyl groups constituting the phenyl Grignard reagent are regioselectively added to surround one 5-membered ring of fullerene C60 (C60Ph5H), can be quantitatively obtained (e.g., Japanese Laid-Open Patent Publication No. 10-167994 (Patent document 1)).
The method for producing a fullerene derivative using the phenyl Grignard reagent and the organocopper reagent is extremely effective for production of a hexa(organo)fullerene derivative, a hepta(organo)fullerene derivative, a deca(organo)fullerene derivative or the like, realizing a high yield of a product of interest. However, there is a problem that, when synthesizing a fullerene derivative in which the number of substituents added is small (e.g., a mono(organo)fullerene derivative, a di(organo)fullerene derivative, a tri(organo)fullerene derivative, and a tetra(organo)fullerene derivative) using this method, the yield thereof is low.